Tracking the interfacial charge transfer behavior of hydrothermally synthesized ZnO nanostructures via complementary electrogravimetric methods

Abstract

The mechanism of species fluxes during the charge–discharge process in a nanostructured ZnO electrode was studied by a combined methodology of electrochemical quartz-crystal microbalance (EQCM) and ac-electrogravimetry.

Electrochemically Reduced Graphene Oxide‐Sheltered ZnO Nanostructures Showing Enhanced Electrochemical Performance Revealed by an In Situ Electrogravimetric Study

“…Figure 1B,C shows the morphologies of ZnO nanostructures, exhibiting vertically aligned individual nanorods with a length of ≈800 nm. These structures are distinct from the random orientation of the ZnO structures [31] and obtained by a two-step synthesis involving an electrochemically grown seed layer and a subsequent hydrothermal growth. A transparent ultrathin ERGO layer on the top of ZnO nanostructures is achieved by electrochemical reduction of a thin graphene oxide (GO) layer and clearly observed in Figure 1C.…”

“…[28][29][30][31] Further information about these parameters is given in the Supporting Information. K i represents the transfer kinetics of each species while G i is the reciprocal of the transfer resistance (Rt i = 1/FG i ), exhibiting the ease or difficulty in the species transfer at the film/electrolyte interface.…”

“…Both EQCM and ac-electrogravimetry measurements were performed in 0.25 m Na 2 SO 4 containing aqueous electrolyte under nitrogen atmosphere, where a ZnO-or ZnO@ERGO-loaded quartz resonator was used as the working electrode, Ag/AgCl (3 m KCl saturated with AgCl) as the reference electrode and a platinum grid as the counter electrode. [28][29][30][31]) were fitted where a good agreement between the experimental and the theoretical functions in terms of both the shape and the frequencies should be achieved, to consider that these parameters (M i , K i , and G i ) are unique. The mass change (Δm) of the electrode during electrochemical process can be estimated by the microbalance frequency change (Δf) through Sauerbrey equation, [34] i.e., Δf = −C f × Δm, where C f is the experimental sensitivity factor of the quartz crystal resonator (C f = 16.3 × 10 7 Hz g −1 cm 2 ).…”

Specific carbon/iodide interactions in electrochemical capacitors monitored by EQCM technique

“…15 It is well known that in situ techniques, despite being powerful tools, display some technical limitations, such as the need for operation in a three-electrode setup; however, with some efforts, these results might be successfully translated to full-device performance. [16][17][18][19][20] In this context, the adsorption/ desorption of ions monitored by an electrochemical quartz crystal microbalance (EQCM) for a single electrode appears to be advantageous [21][22][23][24] and has already been applied to monitor capacitive [24][25][26][27][28][29] and faradaic charge storage processes. 30 Though, it is widely accepted that for highly porous activated carbon (AC) materials, the ion adsorption process is complex and could encounter several barriers preventing the full material capacity or capacitance from being exploited.…”

Correlation between the interfacial ion dynamics and charge storage properties of poly(ortho-phenylenediamine) electrodes exhibiting high cycling stability

“…In addition to these developments in the use of EQCM based methods in the energy storage domain, here, a non-conventional complementary technique, the so-called ac-electrogravimetry has been proposed to unveil the mechanisms of the ionic exchange process [31][32][33]. It has been demonstrated that highly relevant and complementary information to the classical EQCM can be 5 obtained: (i) kinetics and identification of species transferred between the electrode and the electrolyte, (ii) separation of the different contributions related to the charged and non-charged species involved in the electrochemical processes, (iii) identification of species transferred in opposite flux directions provided that their kinetics are sufficiently different and (iv) variation of the relative concentrations of the species inside the examined material [34][35][36][37][38]. The originality of this method is its ability to discriminate between the interfacial transfer of cations, anions and solvent molecules involved (directly or indirectly) in the charge compensation process which is ultimately related to their charge storage performance.…”